1. Field of the Invention
The present invention relates to an apparatus for examining an anterior-segment of an eye.
2. Description of Related Art
There is an apparatus for obtaining a cross-sectional image of an anterior-segment of an eye by optical-sectioning the anterior-segment with slit light and picking up the image of the optical-sectioned anterior-segment by means of an image-pickup optical system configured based on the Scheimpflug's rule. Based on the obtained cross-sectional image, the shape of each part of the anterior-segment such as a cornea or a crystalline lens, the condition of opacity therein, and the like are examined.
One example of such apparatuses is an apparatus disclosed in U.S. Pat. No. 6,074,063 by the present applicant. This apparatus is used to obtain a retroillumination image of an anterior-segment of an eye first, and to obtain a predetermined or intended cross-sectional image of the anterior-segment based on the retroillumination image. However, it is difficult to grasp each part of the anterior-segment three-dimensionally (stereoscopically) using this apparatus. Accordingly, it is also difficult to grasp the condition of opacity three-dimensionally.
On the other hand, there is also an apparatus disclosed in U.S. Pat. No. 5,512,965. This apparatus is used to provide scanning with slit light extending in a vertical direction of an eye so that the scanning may be provided at regular intervals in a lateral direction of the eye, thereby obtaining a plurality of cross-sectional images of the anterior-segment of the eye, and obtaining the shapes of the front and rear surfaces of a cornea and the thickness of the cornea, or the condition of opacity in the cornea, based on the obtained cross-sectional images. With this apparatus, however, only a cornea may be grasped three-dimensionally. In addition, the condition of the center of a pupil (pupillary area) having a great influence on visual acuity may be grasped only as accurately as the periphery of the pupil.